This application claims the priority of German Patent Application Serial No. 100 13 231.6, filed Mar. 13, 2000.
The present invention relates to a device for controlling a motor-driven hoist for raising and lowering a load.
German Pat. No. DE 42 29 674 C2 discloses a motor-driven hoist having a load-carrying member which can be raised and lowered and is located at the lower end of a traction member. An operator grabs a handle formed at the load-carrying member to maneuver the load. The handle includes two push-button keys respectively provided to execute the functions xe2x80x9craisingxe2x80x9d and xe2x80x9cloweringxe2x80x9d, and actuated by means of swivel buttons via a switching rocker in the form of a two-armed lever. The push-button keys belong to control elements that are actuated from outside. In an inactive ready position, the control elements are deactivated and refrain from transmitting electric control signals. Actuation of one control element generates electric control signals which are transmitted via a respective connection cable to the power controllers of the drive.
In order to be able to compensate the change in length of the traction member, the connection cable is configured as a helix which is guided around the traction member in a helical manner. The helix extends or contracts in response to a change in height of the load-carrying member. The available lift travel is thus restricted to the design of the helix. A further deficiency of this conventional construction is the additional space needed for the connection cable and the risk of damage of the connection cable by the traction member.
German Pat. No. DE 44 12 557 C2 discloses a configuration of a push-button key with sequentially arranged secondary contacts. Control signals for power controllers are generated by permanent magnets, disposed at the stem of the push-button key and interacting with a confronting stationary Hall sensor.
It would be desirable and advantageous to provide an improved device for controlling a motor-driven hoist to obviate prior art shortcomings.
The present invention provides for a device for controlling a motor-driven hoist, which device includes a housing, a power source, secured to the housing, for providing electric energy, a control unit supplied with electric energy from the power source and secured to the housing, with the control unit having control elements operable from outside the housing between an inactive ready position and an active position for delivering control signals, a transmitter supplied with electric energy from the power source and receiving the control signals from the control unit for wireless transmission of the control signals to a receiver operatively connected to a power controller of a drive of the motor-driven hoist, and an activation switch so operatively connected to the power source that actuation of any one of the control elements establishes a supply of electric energy from the power source, whereas the supply of electric energy from the power source is cut, when all the control elements occupy their ready position.
Through the provision of a wireless transmission of instructions by using a transmitter for sending out control signals to a receiver that is positioned at a location distant to the housing and operatively controlled to the power controller, and by integrating for the control elements and the transmitter a power supply which is controlled by the activation switch such that supply of electric energy is established when at least one of the control elements is actuated and cut when all the control elements are inactive, the need for a connection cable is eliminated so that the height of the load-carrying member can be varied unrestrictedly. Damage of such a connection cable is thus no longer an issue. The use of the activation switch ensures a long service life of the power source, as the power supply is ON only as long as one of the control elements is actuated. After actuation, the power supply is cut again. As a result, the power supply is thus separated from the control elements and the transmitter so long as the control elements are in the inactive ready position. The receiver may be supplied with electric energy from the power controllers via a common cable connection.
In a simple embodiment, each of the control elements is capable to energize/de-energize the activation switch during course of its actuation. An embodiment with a single activation switch, operatively connected to all the control elements, is simple in structure. However, it is also possible to provide a plurality of activation switches which are operatively connected to a corresponding one of the control elements, whereby the activation switches and the control elements are placed into one-to-one correspondence. Suitably, each of the control elements is configured as a push-button key so biased by a spring as to seek the ready position.
The embodiment with several control elements and a single activation switch can be implemented in a simple manner by providing a common mechanical connecting member which is placed between the control elements and the activation switch and actuated by any one of the control elements for operating the activation switch.
According to another feature of the present invention, which is ergonomically favorable, an actuating mechanism may be provided for operating two of the control elements, with the actuating mechanism including a rocker in the form of a lever having two lever arms, with one lever arm intended for operation of one of the control elements, e.g. raising of load, and with the other lever arm intended for operation of the other one of the control elements, e.g. lowering of load, and with the actuating mechanism further including a pair of push buttons operatively connected to the rocker for actuating one or the other one of the control elements.
Easy maneuvering of the load can be realized by forming the housing as a handle mounted to the load-carrying member of the hoist.
According to another feature of the present invention, the control signals may be encoded before transmission by the transmitter to prevent interferences. Suitably, the transmitter sends the control signal by means of infrared light, whereby the transmitter and the receiver confront one another and/or the transmitter sends out the instruction at a sufficiently great angle of radiation to ensure a reception by the receiver.
A plurality of drives of one or more hoists can be controlled reliably with the control device according to the present invention, when the control signal contains an address information for the receiver being addressed.